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Publication Abstract from PubMed

Photosystem I (PSI) is a large protein supercomplex that catalyzes the light-dependent oxidation of plastocyanin (or cytochrome c(6) ) and the reduction of ferredoxin. This catalytic reaction is realized by a transmembrane electron transfer chain consisting of primary electron donor (a special chlorophyll (Chl) pair) and electron acceptors A(0) , A(1) , and three Fe(4) S(4) clusters, F(X) , F(A) , and F(B) . Here we report the PSI structure from a Chl d-dominated cyanobacterium Acaryochloris marina at 3.3 A resolution obtained by single-particle cryo-electron microscopy. The A. marina PSI exists as a trimer with three identical monomers. Surprisingly, the structure reveals a unique composition of electron transfer chain in which the primary electron acceptor A(0) is composed of two pheophytin a rather than Chl a found in any other well-known PSI structures. A novel subunit Psa27 is observed in the A. marina PSI structure. In addition, 77 Chls, 13 alpha-carotenes, two phylloquinones, three Fe-S clusters, two phosphatidyl glycerols, and one monogalactosyl-diglyceride were identified in each PSI monomer. Our results provide a structural basis for deciphering the mechanism of photosynthesis in a PSI complex with Chl d as the dominating pigments and absorbing far-red light.

A unique photosystem I reaction center from a chlorophyll d-containing cyanobacterium Acaryochloris marina.,Xu C, Zhu Q, Chen JH, Shen L, Yi X, Huang Z, Wang W, Chen M, Kuang T, Shen JR, Zhang X, Han G J Integr Plant Biol. 2021 Oct;63(10):1740-1752. doi: 10.1111/jipb.13113. Epub , 2021 Jun 24. PMID:34002536^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.